With wide popularization of mobile terminals, spectrum resources required by a wireless communications network have become increasingly strained, and how to improve spectrum utilization efficiency becomes particularly important. Improving system spectrum utilization by increasing a quantity of antennas of a base station in a large-scale multi-input multi-output system, which has been proposed recently, has received extensive attention. In this wireless transmission solution, the base station needs to obtain downlink channel state information to process channel fading and interference between users, so as to complete operations such as precoding, multi-user scheduling, and multi-user pairing, so that the system obtains a higher throughput rate.
In a frequency division duplex system, frequency bands occupied by uplink and downlink channels are different, and generally, frequency responses of the uplink and downlink channels are independent from each other. Therefore, in the frequency division duplex system, a pilot signal needs to be used at a receive end to perform channel estimation, and then channel state information is fed back to a transmit end by using an uplink channel.
In a technical solution in which a terminal performs channel estimation by measuring channel state information in a downlink time-frequency resource, and feeds back a measurement result to a base station, a system capacity is low, and system overheads increase dramatically as a quantity of antennas increases.